mirror of
https://github.com/danog/libtgvoip.git
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5caaaafa42
I'm now using the entire audio processing module from WebRTC as opposed to individual DSP algorithms pulled from there before. Seems to work better this way.
92 lines
3.7 KiB
C++
92 lines
3.7 KiB
C++
/*
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* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/audio_processing/aec3/decimator.h"
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#include <array>
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#include <vector>
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#include "modules/audio_processing/aec3/aec3_common.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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namespace {
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// signal.butter(2, 3400/8000.0, 'lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetLowPassFilterDS2() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f},
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f},
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f}};
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}
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// signal.ellip(6, 1, 40, 1800/8000, btype='lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetLowPassFilterDS4() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{-0.08873842f, 0.99605496f}, {0.75916227f, 0.23841065f}, 0.26250696827f},
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{{0.62273832f, 0.78243018f}, {0.74892112f, 0.5410152f}, 0.26250696827f},
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{{0.71107693f, 0.70311421f}, {0.74895534f, 0.63924616f}, 0.26250696827f}};
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}
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// signal.cheby1(1, 6, [1000/8000, 2000/8000], btype='bandpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetBandPassFilterDS8() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true}};
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}
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// signal.butter(2, 1000/8000.0, 'highpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetHighPassFilter() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{1.f, 0.f}, {0.72712179f, 0.21296904f}, 0.7570763753338849f}};
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}
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetPassThroughFilter() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{};
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}
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} // namespace
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Decimator::Decimator(size_t down_sampling_factor)
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: down_sampling_factor_(down_sampling_factor),
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anti_aliasing_filter_(down_sampling_factor_ == 4
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? GetLowPassFilterDS4()
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: (down_sampling_factor_ == 8
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? GetBandPassFilterDS8()
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: GetLowPassFilterDS2())),
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noise_reduction_filter_(down_sampling_factor_ == 8
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? GetPassThroughFilter()
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: GetHighPassFilter()) {
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RTC_DCHECK(down_sampling_factor_ == 2 || down_sampling_factor_ == 4 ||
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down_sampling_factor_ == 8);
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}
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void Decimator::Decimate(rtc::ArrayView<const float> in,
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rtc::ArrayView<float> out) {
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RTC_DCHECK_EQ(kBlockSize, in.size());
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RTC_DCHECK_EQ(kBlockSize / down_sampling_factor_, out.size());
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std::array<float, kBlockSize> x;
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// Limit the frequency content of the signal to avoid aliasing.
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anti_aliasing_filter_.Process(in, x);
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// Reduce the impact of near-end noise.
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noise_reduction_filter_.Process(x);
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// Downsample the signal.
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for (size_t j = 0, k = 0; j < out.size(); ++j, k += down_sampling_factor_) {
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RTC_DCHECK_GT(kBlockSize, k);
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out[j] = x[k];
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}
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}
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} // namespace webrtc
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